Rofener ice lake
The Rofener Eissee was an ice reservoir that occurred several times in the past in the Ötztal Alps in Tyrol , caused by the advance of the Vernagtferner into the Rofental . When it erupted, it wreaked havoc in the Inn Valley .
Formation of the ice lake
The Vernagtferner , which runs roughly in a north-south direction , which today ends a few kilometers above the transverse Rofental, advanced very quickly to the valley floor several times during the Little Ice Age . In doing so, it accumulated on the Zwerchwand on the opposite side of the Rofental and blocked the path of the Rofenache coming from the Hintereis and Hochjochferner , which formed a lake behind. This could be more than 2 km long and have a volume of over 10 million m³. In contrast to the Gurgler Eissee , the dam did not consist of a compact body of ice, but of loosely piled blocks of ice ( séracs ) into which the tongue of the Vernagnferner had been torn due to the high flow speed. The ice lake often flowed safely below or above the ice dam from, but sometimes it came under pressure from the masses of water to spontaneous rupture of the dam, resulting in a large tidal wave through Rofental and subsequently by the Venter valley and the Ötztal to the Inn Valley spilled and wreaked havoc. Even if hardly any people were killed directly, the harvest failed in the devastated fields and there were famines.
timeline
From the 17th to the 19th centuries there were four documented periods in which the ice lake formed. According to geological findings, the Vernagtferner reached the Rofental around 1300 as well, but nothing has survived of an ice lake. In the years 1820 to 1822, the Vernagtferner reached up to the Rofenache without obstructing its drainage.
The lake formed for three to five consecutive years, after which the Vernagtferner had withdrawn so far that it could no longer damm up the Rofenache. The remnants of the dam survived each time as dead ice for many years .
1599-1601
The earliest known record dates from around 1600. The tongue of the Vernagtferner had grown significantly since 1595, and in 1599 it reached the Rofental and the ice lake began to form. On July 20, 1600, there was an eruption that flooded the Ötztal and turned the Längenfeld Basin into a lake. The lake then filled up again in order to empty itself in the summer of 1601 without causing any damage. The watercolor drawing of the Rofener Eisseee, as it appeared in July 1601, is the oldest known representation of an Alpine glacier. In spite of all the imaginative depiction of the time, a number of details, such as the icebergs floating on the lake, are reproduced realistically. At that time the lake level was at an altitude of around 2260 m , the ice dam on the Zwerchwand reached up to 2275 to 2285 m . The lake was around 1.7 km long, 400 m wide and had a volume of around 11 million m³.
1677-1681
In 1676 a new advance of the glacier is reported, in November 1677 the Vernagtferner reached the Zwerchwand and interrupted the Rofenache. In these years the lake is said to have reached a length of up to 2.3 km, which would correspond to a lake level of about 2290 m . In the summers of 1679 and 1681 the lake emptied slowly without causing major damage, on July 16, 1678 and June 14, 1680 there were spontaneous eruptions.
The outbreak of July 16, 1678 is considered the most catastrophic of all eruptions. The volume dammed at that time was estimated at 10 million m³. There was great destruction in the entire Ötztal, in Sölden houses and footbridges, in Huben almost all houses and the church were destroyed. The Ötztaler Ache dug a new bed with many windings near Huben . In the further course bridges and houses were destroyed and cattle destroyed, a child was killed. This eruption coincided with an eruption of the Fischbach near Längenfeld, which particularly affected the lower Ötztal and the Inn Valley. A wandering lad, Thomann Jöchl from the Zillertal, was held responsible for the eruption together with the Fischbach; he was convicted and executed as a "sorcerer" in 1679 at a trial in Merano with twelve other defendants.
On June 14, 1680 there was another devastating eruption with again severe devastation in the Ötztal, even blocks of ice are said to have been sighted on the Danube . At the beginning of July 1681 the lake level was around 2280 m , by hacking out a channel on the diaphragm wall, the water level was lowered to around 2170 m and the lake was able to drain out without damage.
1771-1774
Although the tongue of the Vernagtferner already reached into the Rofental, the Rofenache still flowed unhindered in the summer of 1771. In the first days of October, the formation of the new reservoir began, which on October 27 already reached a length of 400 m and on November 16 of around 750 m. On August 16, 1772 the dam was over 100 m high, the lake was around 1300 m long, 280 m wide and an estimated 60 m deep. However, the lake found an exit between Zwerchwand and Eisdamm and slowly flowed out around Christmas 1772 and on July 12 and 23, 1773 without causing damage. From New Year 1774 the lake level rose again and the lake reached the Hintereisferner. From June 26th, the lake began to slowly empty itself, until the process accelerated on July 4th and most of the dammed water drained off within 12 hours.
From mid-August to mid-September 1772, Joseph Walcher from Vienna studied the ice lake in detail. In his book News from the Icebergs in Tyrol , published in 1773, he collects clues about the earlier eruptions, describes the phenomena and discusses various relief measures. The book also contains an engraving depicting the situation in the summer of 1772. It shows the extent of the lake as far as the tongue of the Hintereisferner and the tongue of the Vernagnferner broken in Séracs.
The Eissee can also be found in the Atlas Tyrolensis by Peter Anich and Blasius Hueber as “Gewester See so Ano 1678. 1679. u. Completely erupted in 1681 and collected again in 1771 ” . This entry probably comes from the commission sent to Rofental in 1771, which had a copy of the Anich card.
1845-1848
In 1845 the lake began to form again. While it emptied slowly in the summer of 1846, devastating eruptions occurred on June 14, 1845, May 18, 1847 and June 13, 1848. In those years the ice lake was over 1200 m long, about 260 m wide and up to 90 m deep. The volume at the eruption in 1847 is estimated at 10 million m³. The eruption in 1845 was slow at first, then 1.3 million m³ of water emptied within an hour with catastrophic consequences. 18 bridges were destroyed between Vent and Umhausen and several houses in Sölden and Huben. In Vent, the tidal wave is said to have been 10 m high, in Innsbruck , a good 100 km downstream , nine hours after the eruption, the level of the Inn rose by 60 cm, and the area in front of the Golden Roof was under water. In 1846 Archduke Johann traveled to the Ötztal on behalf of the emperor to get an idea of the damage on site.
The Rofener Eissee has not formed since 1848 due to the decline of the Vernagtferner.
Research and Action
Because of the danger of the eruption, there was great interest in the ice lake and the circumstances of its formation from an early stage. The formation and eruption of the ice lake have been extensively studied and documented since the 17th century. The depiction from 1601 is the oldest known depiction of an Alpine glacier, and Joseph Walcher's book is one of the first scientific treatises on glaciers. Today these records provide valuable information about the growth and retreat of the glaciers, which was also closely observed by the local population. As early as 1773 it was recognized that the formation of an ice lake was only threatened if the Vernagtferner and the Guslarferner, which flows into it, advanced at the same time.
The population and the authorities were largely helpless in the face of the outbreaks. In order to avert the danger, petitions and pilgrimages were held , especially by children, and a mass was sometimes held every day on the edge of the glacier. Like many other natural disasters of that time, the outbreak of 1678 was attributed to a “weather maker” who was executed along with other “witch masters”.
But early on, people also thought about draining the water safely from the lake. Attempts were made, in some cases with success, to dig ditches for drainage in the ice masses. Other suggestions included drilling through the dam with a drill, blasting the dam with a mine, or bombarding it with cannons. The construction of a hermitage in the Venter Valley was also considered, as was the construction of a tunnel through the diaphragm, which could also allow drainage in the event of future closures. Joseph Walcher discussed all of these possibilities in his book and dismissed most of them as too dangerous, impractical or ineffective.
literature
- Hans Haid : About glacier bans, petitions, sharp vows, children's processions to the far etc. In: R. Lackner, R. Psenner, M. Walcher (eds.): Is it the Sindt river? Cultural strategies & reflections for the prevention and management of natural hazards. alpine space - man & environment, Vol. 4. Innsbruck University Press, Innsbruck 2008, ISBN 978-3-902571-32-8 , pp. 75-84. ( PDF; 299 kB ).
- Hans Kinzl : The representation of the glaciers in the Atlas Tyrolensis by Peter Anich and Blasius Hueber (1774) . In: R. v. Klebelsberg-Festschrift of the Geological Society in Vienna, Volume 48 of the communications of the Austrian Geological Society, 1955, pp. 89-104. ( PDF; 1.7 MB ).
- E. Leys, O. Reinwarth: Effects of the glaciers and the glacier runoff on the torrent and avalanche danger and their consideration in the hazard zone plans. In: Interpraevent, Volume 1 (1975), pp. 345-357. ( PDF; 3.3 MB ).
- H. Moser, H. Escher-Vetter, H. Oerter, O. Reinwarth, D. Zunke: Runoff in and from glaciers. GSF report 41/86, Part I, Society for Radiation and Environmental Research, Neuherberg 1986, hdl : 10013 / epic.38511 .
- Kurt Nicolussi: On the history of the Vernagtferner - glacier advances and lake eruptions in the past millennium. In: Eva-Maria Koch, Brigitta Verschbamer (eds.): Climate, Weather, Glaciers in Transition. Alpine Research Center Obergurgl, Volume 3, innsbruck university press, Innsbruck 2013, ISBN 978-3-902811-89-9 , pp. 69–94. ( PDF; 3 MB ).
- Eduard Richter : On the history of the Vernagt glacier. Contributions to the history and geography of the Alps. IV. In: Journal of the German and Austrian Alpine Association, year 1877, Volume VIII, pp. 164–168. ( Digitized version ).
- Walter Senarclens-Grancy: On the glacial geology of the Oetztal and its surroundings. In: Mitteilungen der Geologische Gesellschaft in Wien, Volume 49, 1956 pp. 257–314. ( PDF; 17.9 MB ).
- Michael Stotter: The glaciers of the Vernagtthales in Tyrol and their history. Innsbruck 1846. ( digitized version ).
- Joseph Walcher : News from the icebergs in Tyrol. Vienna 1773. ( digitized version ).
Web links
- Tirol Atlas - Naturchronik Tirol - Keyword search Rofener Eissee
- Dept. of Glaciology of the Commission for Earth Measurement and Glaciology of the BAdW-Munich: Contemporary representation of the Rofener Ice Lake dammed by the Vernagtferner
Coordinates: 46 ° 49 ′ 52 ″ N , 10 ° 50 ′ 59 ″ E